Select edge ring in UV mode?
OK, so it seems fair to answer this - since the question was about selecting edge ring in UV editor. 

The way to do this is by:


enabling "keep UVs and edit mode mesh selection in sync" (button in the header of UV editor)
just Ctrl+Alt+RMB an edge in 3D editor (a derived UV selection will show up in UV editor)


Were the question about straightening the resulting selection, it would seem there is no way to do this for now (version 2.67b).

[Thanks to Mr Zak for clearing the confusion.]